Question: Suppose the area of a circle is ${64\pi}$. What is its circumference?
${K = 64\pi}$ ${c = 16\pi}$ First, find the radius: $K = \pi r^2$ , so $r = \sqrt{K / \pi} = \sqrt{{64\pi} / \pi} = {8}$ Now find the circumference: $c = 2\pi r = 2\pi \cdot {8} = {16\pi}$.